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J/ApJ/836/232        Swift-UVOT obs. analysis of 29 SNe Ia        (Brown+, 2017)

Reddened, redshifted, or intrinsically red? Understanding near-ultraviolet colors of Type Ia supernovae. Brown P.J., Landez N.J., Milne P.A., Stritzinger M.D. <Astrophys. J., 836, 232-232 (2017)> =2017ApJ...836..232B (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry, ultraviolet ; Photometry, UBV Keywords: dust, extinction; supernovae: general; supernovae: individual: (SN2011fe, SN2011ia); ultraviolet: general Abstract: The intrinsic colors of Type Ia supernovae (SNe Ia) are important to understanding their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the intrinsic spectrum, the filter curves, and the wavelength dependence of reddening. We present ultraviolet and optical data of a growing sample of SNe Ia observed with the Ultraviolet/Optical Telescope on the Swift spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find that a small amount of reddening (E(B-V)=0.2mag) could account for the difference between groups designated as NUV-blue and NUV-red, and a moderate amount of reddening (E(B-V)=0.5mag) could account for the whole NUV-optical differences. The reddening scenario, however, is inconsistent with the mid-UV colors and color evolution. The effect of redshift alone only accounts for part of the variation. Using a spectral template of SN2011fe, we can forward model the effects of redshift and reddening and directly compare those with the observed colors. We find that some SNe are consistent with reddened versions of SN2011fe, but most SNe Ia are much redder in the uvw1-v color than SN2011fe reddened to the same b-v color. The absolute magnitudes show that two out of five NUV-blue SNe Ia are blue because their near-UV luminosity is high, and the other three are optically fainter. We also show that SN 2011fe is not a "normal" SN Ia in the UV, but has colors placing it at the blue extreme of our sample. Description: Swift/UVOT has observed over 500 SNe of all types in its 12 years of operation (see Brown+ 2015JHEAp...7..111B for a review of the first 10yrs). Most of the observations use six UV and optical filters. All photometry comes from the Swift Optical/Ultraviolet Supernova Archive (SOUSA; Brown+ 2014Ap&SS.354...89B) and is available at the Swift SN website and the Open Supernova Archive (Guillochon+ 2017ApJ...835...64G). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 124 29 Supernovae Ia information
See also: J/AJ/131/527 : UBVRI light curves of 44 type Ia supernovae (Jha+, 2006) J/ApJ/659/122 : Improved distances to type Ia supernovae (Jha+, 2007) J/ApJ/689/377 : PAIRITEL SNe Ia as NIR standard candles (Wood-Vasey+, 2008) J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009) J/ApJS/185/32 : First-year SDSS-II SN results (Kessler+, 2009) J/ApJ/721/1608 : Absolute UV magnitudes of type Ia SNe (Brown+, 2010) J/AJ/139/120 : Low-redshift Type-Ia supernovae (Folatelli+, 2010) J/ApJ/731/120 : Intrinsic SN Ia light curves (Mandel+, 2011) J/ApJ/753/22 : Swift/UVOT observations of SN 2011fe (Brown+, 2012) J/A+A/554/A27 : 2011fe spectrophotometric time series (Pereira+, 2013) J/A+A/568/A22 : Joint analysis of the SDSS-II and SNLS SNe Ia (Betoule+, 2014) J/ApJS/212/18 : An atlas of UV-to-MIR galaxy SEDs (Brown+, 2014) J/ApJ/796/L18 : Type Ia supernova 2011de UVOT photometry (Brown, 2014) J/MNRAS/438/1391 : Host galaxies of Type Ia SN from PTF (Pan+, 2014) J/AJ/152/102 : Flux conversion factors for Swift/UVOT filters (Brown+, 2016) J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016) : Swift SNe webpage : The online Open Supernova Catalog Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Name Supernova identifier 11- 14 F4.2 mag Dm15B [1/1.4] The B band decline rate parameter (1) 16- 19 F4.2 mag e_Dm15B [0.01/0.2] Uncertainty in Dm15B 21- 26 F6.3 mag w1mag [11/18.8] Swift/UVOT w1 band magnitude at B band peak 28- 32 F5.3 mag e_w1mag [0.001/0.2] Uncertainty in w1mag 34- 39 F6.3 mag Vmag [10/17] The Johnson V band magnitude at B band peak 41- 45 F5.3 mag e_Vmag [0.001/0.03] Uncertainty in Vmag 47- 52 F6.3 mag B-V The (B-V) color index at B band peak 54- 58 F5.3 mag e_B-V Uncertainty in (B-V) 60- 65 F6.3 mag DM [29.1/35.6] Distance modulus 67- 71 F5.3 mag e_DM [0.04/0.4] Uncertainty in DM 73- 80 A8 --- n_DM Method used to derive DB (2) 82-124 A43 --- r_DM Reference for DM
Note (1): Decline in the B band from 15 days after maximum. Note (2): z = redshift distance is derived using the referenced recessional velocity corrected for the galaxy-flow model of Mould+ (2000ApJ...529..786M) implemented by the NASA Extragalactic Database (NED) and converted to a distance modulus assuming H0=72km/s/Mpc Freedman+ (2001ApJ...553...47F). SBF = surface brightness fluctuation (1 occurrence)
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Oct-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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